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Electronic circuit deviceRelated Patent Categories: Electricity: Conductors And Insulators, Conduits, Cables Or Conductors, Preformed Panel Circuit Arrangement (e.g., Printed Circuit), With Particular Conductive Connection (e.g., Crossover)Electronic circuit device description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060032669, Electronic circuit device. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCES TO RELATED APPLICATIONS [0001] The present invention contains subject matter related to Japanese Patent Application JP 2004-234052 filed in the Japanese Patent Office on Aug. 11, 2004, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to electronic circuit devices, and particularly relates to an electronic circuit device capable of mounting electronic components at high density. [0004] 2. Description of the Related Art [0005] In the field of mobile terminals and information appliances, electronic circuit devices composed of multilayer substrates capable of achieving higher packing densities have been used, as disclosed in PCT Japanese Translation Patent Publication No. 7-107954. The demand on such electronic circuit devices for size and weight reductions and higher functions has been increasing in recent years. [0006] According to the demand, flexible cables and substrates, which can be bended, are often used to connect the above multilayer substrates. [0007] FIG. 1 shows a top view (upper) and a longitudinal sectional view (lower) of an example of a rigid substrate and a flexible cable connected thereto with a connector. [0008] In FIG. 1, a rigid substrate 1 includes three laminated insulating boards, such as glass-epoxy boards, having an electrical circuit made of copper foil. A flexible cable 2 is made of a polyimide film instead of an insulating board. The flexible cable 2 is used to connect the rigid substrate 1 to, for example, an external interface or another substrate (not shown). [0009] The flexible cable 2 is connected to a right end region 1b of the top surface 1a of the rigid substrate 1 with a connector 3. That is, the region 1b of the top surface la of the rigid substrate 1 is assigned to the connector 3 to connect the flexible cable 2 to the rigid substrate 1. As a result, other electronic components such as semiconductor chips and resistors cannot be mounted in the right end region 1b. The rigid substrate 1 therefore has difficulty in providing electronic circuit devices with higher densities. Accordingly, a rigid/flexible substrate and a multilayer flexible substrate as shown in FIGS. 2A and 2B are used to eliminate the need for the connector 3. [0010] FIG. 2A shows a top view (upper) and a longitudinal sectional view (lower) of an example of a rigid/flexible substrate. FIG. 2B shows a top view (upper) and a longitudinal sectional view (lower) of an example of a multilayer flexible substrate. [0011] In FIG. 2A, a rigid/flexible substrate 11 includes two rigid boards 21-1 and 21-2 laminated with a flexible board 22 disposed therebetween. The flexible board 22 is longer than the rigid boards 21-1 and 21-2 by the length of a cable part (connection part) 22a for connection to another substrate. Unlike the flexible cable 2, the rigid/flexible substrate 11 has no connector so that electronic components can be mounted on the overall top surface 21a of the rigid board 21-1. [0012] In FIG. 2B, a multilayer flexible substrate 12 includes two flexible boards 31-1 and 31-2 laminated with another flexible board 32 disposed therebetween. The flexible board 32 is longer than the flexible boards 31-1 and 31-2 by the length of a cable part (connection part) 32a for connection to another substrate. That is, the multilayer flexible substrate 12 differs from the rigid/flexible substrate 11 only in that the flexible boards 31-1 and 31-2 are used instead of the rigid boards 21-1 and 21-2. Accordingly, unlike the flexible cable 2, the multilayer flexible substrate 12 has no connector so that electronic components can be mounted on the overall top surface 31a of the flexible board 31-1. [0013] There is another approach to eliminating the use of a connector. FIG. 3 shows a top view (upper) and a longitudinal sectional view (lower) of an example of a rigid substrate. [0014] In FIG. 3, a flexible cable 42 is partially bonded directly to a right end region 41b of the top surface 41a of a three-layer rigid substrate 41 with, for example, solder or an anisotropic conductive film. The direct bonding of the flexible cable 42 to the rigid substrate 41 is used as one of the approaches to eliminating the use of a connector. SUMMARY OF THE INVENTION [0015] However, flexible cables and boards as described above, which are made of polyimide, are more costly than rigid boards, which are, for example, glass epoxy boards. [0016] If, therefore, the rigid/flexible substrate 11 in FIG. 2A is used to provide higher-density electronic circuit devices with no connector, the flexible board 22 is used, which has a size equivalent to the sum of the sizes of the rigid boards 21-1 and 21-2 and the cable part 22a. If the multilayer flexible substrate 12 in FIG. 2B is used, the flexible boards 31-1 and 31-2 are used in addition to the flexible board 32. Thus, the use of the rigid/flexible substrate 11 or the multilayer flexible substrate 12 for achieving higher densities disadvantageously results in higher cost. [0017] If the flexible cable 42 is bonded directly to the rigid substrate 41, as shown in FIG. 3, electronic components cannot be mounted in the region 41b used for partially connecting the flexible cable 42 on the top surface 41a of the rigid substrate 41, though the region 41b is smaller than the region 1b used for connecting the connector 3 in FIG. 1. [0018] Under the above circumstances, it is desirable to provide an electronic circuit device capable of mounting electronic components at high density with no increase in cost. [0019] An electronic circuit device according to an embodiment of the present invention includes at least two circuit substrates and a flexible board for external electrical connection disposed between the circuit substrates. The flexible board is electrically connected to at least the surface of one circuit substrate opposed to another circuit substrate. [0020] The flexible board may be electrically and physically connected to a predetermined region of the surface of the one circuit substrate with a solder, a metal paste, or an anisotropic conductive adhesive. [0021] The electronic circuit device may further include a spacer board disposed between the circuit substrates. The spacer board connects the circuit substrates to each other. Continue reading about Electronic circuit device... Full patent description for Electronic circuit device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electronic circuit device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Electronic circuit device or other areas of interest. ### Previous Patent Application: Printed circuit boards and method of producing the same Next Patent Application: Connection structures for microelectronic devices and methods for forming such structures Industry Class: Electricity: conductors and insulators ### FreshPatents.com Support Thank you for viewing the Electronic circuit device patent info. 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